A power supply creates a voltage difference between high and low power supply rails. The power supply has a voltage signal source, a capacitive coupling element, energy storage element 12, first and second rectifying diodes, a regulator, and bypass means for selectively decreasing the impedance between the voltage signal source and the low power supply rail or increasing the load presented to the voltage signal source. The capacitive coupling element is connected to the voltage signal source. Energy storage element 12 stores energy between the high and low power supply rails. The first rectifying diode is positioned between the capacitive coupling element and energy storage element 12. It is coupled to the voltage signal source through the capacitive coupling element and arranged to favor current flow toward energy storage element 12 from the capacitive coupling element. The second rectifying diode is positioned between the capacitive coupling element and the low power supply rail. It is coupled to the voltage signal source through the capacitive coupling element and arranged to favor current flow toward the capacitive coupling element from the low power supply rail. The regulator regulates the level of energy stored in energy storage element 12.